1. Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
2. Physics Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
3. Climate and Space Sciences and Engineering Department, University of Michigan, Ann Arbor, Michigan 48109, USA
4. Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA